how to calculate input impedance of load (patch etc) in HFSS

Dear All
I am sure this thing has been discussed many times and after reading a number of posts with confusing comments i am writing this for our help. Please correct me if i am wrong any where.

Let me first define the port Zo, this variable is related to the characteristics impedance of the port or precisely the characteristic impedance of the mode that is being launched into the system using port.

input impedance:
Since we all require the input impedance of the of test structures e.g patch antenna or any filter etc. We CAN NOT directly read the input impedance of structure. The Z matrix (Z11) tells us the input impedance of whole system at port when watching towards load. This includes the input impedance of structure as well as the feeding line. In case of mismatched feed line and structure the Z11 will no where close to the input impedance of structure.

How to calculate input impedance of structure:
The structure for which impedance is required, feed it with any transmission line with characteristic impedance Zo (50 if you like) and any known e-length, now simulate and get Z11, this Z11 is the transformed impedance. Use impedance transformation relation and transform impedance back to load position to calculate the impedance of load. (-ive l to be used)

Alternatively use smith chart put the value of input system impedance (Z11) and move towards load, read the value from constant VSWR circle and multiply it with impedance of feeding line. this will give you impedance of load

I hope this issue will be resolved by now.

Regards
FS